Right off the bat please resist saying when the boat won't start.
Here is what is going on, the boat is a 1990 Maristar, two weeks ago I uncovered the boat turned the key and nothing happened, not a sound or click. I turned the key a few more times, still nothing and then it fired right up and started without a problem for the rest of the day. Last week the same thing, the starter is about 6 years old and solenoid is three years old. My first thought was the battery (it's 5 years old) and had that replaced. Was not the problem, yesterday I replaced the solenoid and the boat started this morning when cold so I think this issue is solved.
However while the solenoid was off I noticed the round piece of the starter that slips into the spring of the solenoid was discolored. It was actually the same color of inside of the solenoid.
Is this a sign the starter is going bad?, any information would be helpful.
Also is there anyone out there with an older boat that has replaced the starter by them self? Not sure I want to dig in that deep.

I hope the solenoid was the problem and it is fixed. Starter problems are terrible. I had to replace the the ignition switch on my 89 and then again on my 85. It was the last thing I did both times and both times that was the issue. I still have a really nice rebuilt 4160 Holley Carb for a 454 sitting on a shelf if you need one, as well as a mallory points distributor. I will probably post them on this site for cheap one of these days.